Plasma processing method

ABSTRACT

A plasma processing method utilizing a plasma processing apparatus having a plasma generating unit, a process chamber including an outer cylinder for withstanding a reduced pressure, and an inner cylinder made of non-magnetic material and being replaceable arranged inside the outer cylinder, a process gas supply unit for supplying gas to the process chamber, a specimen table for holding a specimen and a vacuum pumping unit. A temperature of the inner cylinder is monitored, and a desired inner cylinder temperature which is inputted in advance in response to a processing condition of the specimen is compared with the monitored temperature of the inner cylinder. A temperature of the outer cylinder is controlled in response to a result of the comparison so as to control the inner cylinder temperature to a predetermined value.

CROSS REFERENCE TO RELATED APPLICATION

This is a continuation of U.S. application Ser. No. 10/617,019, filedJul. 11, 2003, now abandoned, which relates to U.S. application Ser. No.10/617,020, filed Jul. 11, 2003, now abandoned, which are continuationsof U.S. application Ser. No. 09/983,946, filed Oct. 26, 2001, now U.S.Pat. No. 6,815,365, which relates to U.S. application Ser. No.10/647,319, filed Aug. 26, 2003, now abandoned which is a continuationof U.S. application Ser. No. 09/984,052, filed Oct. 26, 2001, whichrelates to U.S. application Ser. No. 10/441,009, filed May 20, 2003,which is a continuation of U.S. application Ser. No. 09/421,044, filedOct. 20, 1999, now abandoned, which relates to U.S. application Ser. No.10/253,862, filed Sep. 25, 2002, which is a continuation of U.S.application Ser. No. 09/984,052, filed Oct. 26, 2001, now abandoned,which relates to U.S. application Ser. No. 09/421,044, filed Oct. 20,1999, now abandoned, which is a continuation of U.S. application Ser.No. 09/983,946, filed Oct. 26, 2001, now U.S. Pat. No. 6,815.365, whichrelates to U.S. application Ser. No. 09/984,052, filed Oct. 26, 2001,now abandoned, which is a continuation of U.S. application Ser. No.09/421,043, filed Oct. 20, 1999, which is a continuation of U.S.application Ser. No. 09/227,332, filed Jan. 8, 1999, now U.S. Pat. No.6,171,438, which is a continuation-in-part of U.S. application Ser. No.08/611,758, filed Mar. 8, 1996, now U.S. Pat. No. 5,874,012, the subjectmatter of U.S. application Ser. No. 08/611,758 being incorporated byreference herein.

BACKGROUND OF THE INVENTION

The present invention relates to a plasma processing apparatus and aplasma processing method; and, more particularly, the invention relatesto a plasma processing apparatus and a plasma processing method suitablefor processing a specimen, such as etching a specimen using a highdensity plasma.

In a conventional plasma processing apparatus, as described, forexample, in Kanno, T., Semiconductor Plasma Processing Technology,Sangyou-Tosho Company (1980), page 139, using a microwave plasmaprocessing apparatus, which has a quartz discharge chamber in awaveguide transmitting a microwave, plasma is generated in the dischargechamber by action of an outer magnetic field generated by a coilarranged outside of the discharge chamber and a microwave electricfield. Thereby, processing, such as etching of a surface of asemiconductor wafer, can be performed using the plasma.

For a processing chamber in such a microwave etching apparatus, anon-magnetic and conductive material used as the waveguide is necessaryto guide the microwave energy and to introduce the outer magnetic fieldin the processing chamber. Therefore, a metal, such as aluminum (A1) ora stainless steel (SUS), is commonly used for the wall material of theprocessing chamber.

However, a metal, such as a stainless steel or the like, composing thewall surface of the processing chamber, becomes worn and dispersed bythe plasma, and the heavy weight metals contained in the material becomea contamination source.

A technology is disclosed in Japanese Patent Application Laid-Open No.4-229619 (1992) where a conductive coating film capable of protecting ametallic surface from chemical corrosion by a reaction gas used in aprocessing chamber is formed on the metallic inner surface. Inaccordance with this technology, a protective film is formed on themetallic inner wall surface of the processing chamber through coating,since the metallic inner wall surface may be corroded when plasmaetching is performed by using a halogen gas, such as chlorine, as theprocessing gas. Aluminum is used as the material for the processingchamber, and TiN, InSn, SiC, TiC, TaC or the like is used for thecoating material. The thickness of the coating film is 0.2 μm to 1 μm.

Further, a dry etching apparatus having opposed electrodes inside achamber is disclosed in Japanese Patent Application Laid-Open No.63-138737 (1988), wherein the inside surface of the chamber is coveredwith an insulator material detachable from the chamber in order to keepa contaminated inner surface of the chamber clean. As the insulatormaterial, there is used alumite, alumina thermal spraying, teflon,ceramic or the like.

The above conventional technology disclosed in Japanese PatentApplication Laid-Open No. 4-229619 (1992) can protect the metallicsurface from chemical corrosion due to the reaction gas used in theprocessing chamber. However, as for the typical condition of the plasmaetching process, it is clear that the temperature during plasmaprocessing is limited to a relatively low temperature range ofapproximately 10° C. to approximately 70° C. The reason why thistemperature limitation is set seems to be that cracks may occur in thecoating film on the aluminum surface due to the thermal expansion of thealuminum if the temperature of the aluminum composing the processchamber rises above 100° C. during plasma processing. In order to avoidthe occurrence of cracks, the thickness of the coating film must bereduced. However, if the thickness of the film is reduced, the coatingfilm cannot perform its function, since it will be corroded out in ashort time by the reaction gas generated during plasma etching. Forexample, data according to an experiment conducted by the inventorsshows that an SiC film is worn off at a speed of approximately 0.05μm/minute during etching. This means that a coating film having athickness of 0.2 μm to 1 μm is damaged and eliminated in several hours,that is, during a time when several hundreds of specimens have beenprocessed. As a result, the metallic surface of the inner wall of theprocess chamber is exposed to the plasma and worn off by the plasma orhas its quality altered due to chemical reaction. The worn-off metalbecomes a heavy metal contamination source and the quality-alteredmetallic wall degrades the characteristic of the process chamber.

On the other hand, in the invention disclosed in Japanese PatentApplication Laid-Open No. 63-138737 (1988), a contaminated isolatormember is dismounted from a chamber and cleaned, and then re-mounted inthe chamber to be used again. However, in a system where an insulatormember is mounted onto the inner surface of a chamber, there is aproblem in that the plasma processing characteristic largely fluctuatesbecause the temperature of the mounted insulator member fluctuatesduring plasma processing.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a plasma processingapparatus and a plasma processing method in which the characteristic ofplasma processing is stabilized over time by preventing the innersurface of the process chamber from having its quality altered and frombecoming a heavy metal contamination source, and by maintaining thetemperature of the inner surface of the process chamber at a giventemperature.

The present invention is characterized by a plasma processing apparatuscomprising a plasma generating unit, a process chamber capable of havingits inside pressure reduced, a process gas supply unit for supplying agas to the process chamber, a specimen table for holding a specimen, anda vacuum pumping unit, wherein

the process chamber comprises an outer cylinder having the capability ofwithstanding a reduced pressure, an inner cylinder arranged inside theouter cylinder through a gap, and a temperature controlling means formaintaining the temperature of the inner cylinder within a giventemperature range.

The present invention is also characterized by a plasma processingapparatus as described above, wherein the process chamber comprises anouter cylinder having the capability of withstanding a reduced pressure,an inner cylinder arranged inside the outer cylinder through a gap, atemperature controlling means arranged in the outer cylinder, and a heattransmission means for transmitting heat between the outer cylinder andthe inner cylinder arranged in the gap.

Further, the present invention is characterized by a plasma processingmethod of processing a specimen using a plasma processing apparatuscomprising a plasma generating unit, a process chamber capable of havingits inside pressure reduced, a process gas supply unit for supplying agas to the process chamber, a specimen table for holding a specimen, anda vacuum pumping unit, wherein the process chamber comprises an outercylinder having the capability of withstanding a reduced pressure, aninner cylinder arranged inside the outer cylinder through a gap, atemperature controlling means arranged in the outer cylinder, and a heattransmission means for transmitting heat between the outer cylinder andthe inner cylinder arranged in the gap, and wherein plasma processing isperformed on the specimen while the temperature of the inner cylinder isbeing kept within a given temperature range.

Still further, the present invention is characterized by a plasmaprocessing method as described above, wherein the inner cylinder is madeof a non-magnetic material not containing heavy metals, or is made of amaterial selected from a group of ceramic, carbon, silicon, quartz andmetal materials, and plasma processing is performed on said specimenwhile the temperature of said inner cylinder is being kept within agiven temperature range.

According to the present invention, since the inner cylinder used as theinner wall of the process chamber, which is made of a material notcontaining heavy metals, such as a ceramic, a metallic surface such asaluminum composing the outer cylinder is not exposed during theprocessing of a wafer. Therefore, the wall never becomes a heavy metalcontamination source by being worn or changed in quality by the plasma.On the other hand, since the thermal conductivity of the inner cylinderis lower than that of the outer cylinder, the temperature of the innercylinder, that is, the surface temperature of the process chamber, maybe raised up to 200° C. to 350° C. during etching process if thetemperature is not controlled. In accordance with the present invention,since the temperature of the inner cylinder is controlled to a desiredtemperature, for example, a desired temperature between 100° C. to 350°C., the surface temperature of the process chamber can be kept to adesired temperature and the etching characteristic is also kept stable.

Further, it is also possible to stabilize the process by controlling thesurface temperature of the inner cylinder in a desired pattern.

Furthermore, in a case of employing such a material composing thecylinder that the inner side surface of the material is worn bit by bitby plasma, since the inside surface of the inner cylinder is alwaysrenewed to a new surface, there is no worry about contamination due to achange in quality of the inside surface, and accordingly there is notime-change in the characteristic of the process chamber. In addition tothis, since the inner cylinder does not contain any heavy metals, thereis no worry that the inner cylinder becomes a contamination source evenif it is worn.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partial cross-sectional vertical front view showing anembodiment of a microwave plasma processing apparatus in accordance withthe present invention.

FIG. 2 is an enlarged view showing the main part of the temperaturecontroller for the inner cylinder shown in FIG. 1.

FIG. 3 is a graph showing the function of the temperature controller ofFIG. 1.

FIG. 4 is a graph showing the relationship between gap pressure P andtemperature difference in the temperature control.

FIG. 5 is a vertical cross-sectional view showing a second embodiment ofa microwave plasma processing apparatus in accordance with the presentinvention.

FIG. 6 is a transverse cross-sectional view showing the main part of theplasma processing apparatus of FIG. 5.

FIG. 7 is a vertical cross-sectional view showing a third embodiment ofa parallel plate plasma etching apparatus in accordance with the presentinvention.

FIG. 8 is a cross-sectional view showing an example of a magnetron RIEapparatus to which the present invention is applied.

FIG. 9 is a cross-sectional view showing an example of a plasmaprocessing apparatus to which the present invention is applied, theplasma processing apparatus being of an external energy supplyingdischarge type, and particularly of an induction coupling discharge typeand a non-magnetic field type.

FIG. 10 is a cross-sectional view showing an example of a plasmaprocessing apparatus to which the present invention is applied, theplasma processing apparatus being of an external energy supplyingdischarge type, and particularly of an induction coupling discharge typeand a magnetic field type.

FIG. 11 is a cross-sectional view showing an example of a plasmaprocessing apparatus to which the present invention is applied, theplasma processing apparatus being of an external energy supplyingdischarge type, and particularly of an induction coupling discharge typeand a magnetic field type.

FIG. 12 is a vertical cross-sectional view showing an example of asample to be processed with an apparatus in accordance of the presentinvention, the sample being a resist attached oxide film.

FIG. 13 is a graph showing the relationship between a number ofprocessed wafers and the temperature of the inner cylinder.

FIG. 14 is a cross-sectional view showing an embodiment of a sampletable cover portion of a plasma processing apparatus to which thepresent invention is applied.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention will be described in detail below,referring to the accompanying drawings.

FIG. 1 is a partial cross-sectional vertical front view showing anembodiment of a microwave plasma processing apparatus in accordance withthe present invention, and FIG. 2 is an enlarged view showing the mainpart of the apparatus. The reference character 1 designates a magnetronoperating as a microwave oscillator source, and the reference character2 designates a guide tube for microwave energy. The reference character3 designates a quartz plate for permitting the supply of microwaveenergy to a process chamber 4 while vacuum sealing the process chamber4. The process chamber 4 is composed of an outer cylinder 5 made of, forexample, high purity aluminum (A1) and is capable of withstandingdepressurization, and an inner cylinder 6 arranged inside the outercylinder and made of ceramic, such as silicon carbide (SIC) or the like.Since the inside surface of the process chamber is formed of aninsulator and the outer side is formed of a conductor, the processchamber 4 also serves as a waveguide. The reference character 7designates a first solenoid coil for supplying a magnetic field, and thereference character 8 (8A, 8B) designates a second solenoid coil. Theprocess chamber 4 is evacuated to vacuum by a vacuum pump connected to avacuum chamber 9. The reference character 10 designates a sample tablefor mounting a wafer 11 to be processed, for example, to be etched, andconnected to a high frequency power source 12. The reference character13 designates a process gas supplying system which supplies a processgas for performing processing, such as etching, film forming or thelike, into the process chamber 4.

There is a gap G14 having an interval of nearly 0.1 to 2 mm between theinner cylinder 6 and the outer cylinder 5, and a heat transfer gas fortemperature control is introduced into the gap through a gas supplysystem 15. The gas supply system 15 has a gas source 16, a pressurecontrol valve 17, a pressure detector 18, a pressure command instructionmeans 19 and a controller 20. The pressure P between the gap 14 isdetected by the pressure detector 18 and the opening of the pressurecontrol valve 17 is controlled so as to keep the pressure P at a desiredvalue.

The inner cylinder 6 is supported by a supporter 32. In order to replacethe inner cylinder when its surface is worn a certain amount, the innercylinder is detachably supported by the outer cylinder.

A heater 21 for heating the process chamber 4 is arranged around theouter cylinder 5, and the temperature T of the inner cylinder 6 isdetected by a temperature detector 23. A controller 22 controls thetemperature of the outer cylinder 5 to a temperature T₀. The heater 21works to maintain the temperature T of the inner cylinder 6 by keepingthe temperature T₀ of the outer cylinder 5 and the pressure of the gapat preset values.

During plasma processing, the pressure of the process chamber 4 isadjusted to a preset process pressure by introducing a process gas intothe process chamber 4 from the gas supply system 13 at a given flow ratewhile vacuum evacuating the chamber using the vacuum pump. Further, thetemperature T₀ of the outer cylinder 5, the temperature T of the innercylinder 6 and the pressure P of the gap 14 are controlled by the heater21, the gas supply system 15 and the temperature controller 22.

A wafer 11 to be processed is mounted so as to be held on the sampletable 10. The magnetron 1 and the first and the second coils 7, 8 areswitched on, so that a microwave is guided to the process chamber 4, andthen plasma 100 is generated in the process chamber 4 to etch the wafer11.

According to the present invention, since no metallic surface, such asaluminum, forms an exposed inside wall of the process chamber 4, thereis no possibility that a metal part will become worn and varied inquality, and so the wall cannot become a heavy metal contaminationsource to the wafer 11.

On the other hand, the SiC inner surface of the inner cylinder 6 is wornby plasma 100 bit by bit. However, since the SiC cylinder does notcontains any heavy metal, there is no worry that the cylinder becomes acontamination source even if it is worn. On the contrary, since theinner surface of the inner cylinder is always renewed to a new surfaceas it is being worn, there is no worry about contamination due tovarying the quality of the inside surface, and accordingly thecharacteristic of the process chamber 4 hardly varies with time. Theworn SiC component is exhausted from the process chamber 4 by the vacuumpump.

The temperature of the inner cylinder is increased by heat generated inthe process chamber during the etching process. If it is not controlled,the temperature T of the inner cylinder will reach up to 200° C. to 350°C. or higher. On the other hand, the etching characteristic in a plasmaetching process is strongly affected by the temperature of the insidesurface. In other words, since reaction between the inner cylinder 6 andthe etching gas varies depending on the change in the surfacetemperature of the inner cylinder 6 and causes fluctuation in etchinggas environment, the etching characteristic is not stabilized. Forexample, since the temperature change of the inner surface 6 causes thecomponent, to fluctuate and the amount of accumulated materials on thewall and the change in the reaction speed with the wall causes thecomponent in the plasma to fluctuate, the etching characteristic is notstabilized.

In accordance with the present invention, the surface temperature T ofthe inner cylinder is controlled to a desired value in the range of 100°C. to 350° C., preferably 150° C. to 300° C., by controlling thetemperature T₀ of the outer cylinder 5 using the heater 21 and thepressure P in the gap 14. According to the present invention, since thesurface temperature T of the inner cylinder 6 is kept at a preset value,the etching characteristic becomes stable. Further, since the surfacetemperature T of the inner cylinder 6 is kept at a preset value and theetching speed to the inside surface of the inner cylinder 6 isstabilized, the wearing rate of the surface of the inner cylinder 6,which is worn by the plasma, also becomes constant. Thereby, thecharacteristic of the process chamber 4 becomes stable.

FIG. 3 shows the function for controlling the temperature of the innercylinder 6 as carried out by the temperature controller 22. As anexample, the figure shows a case where the temperature T of the innercylinder 6 is caused to approach T₀ by keeping the temperature of theouter cylinder 5 at T₀.

In this case, as shown in FIG. 4, the temperature difference between Tand T₀ can be decreased by increasing the pressure P in the gap 14. Inmore detail, in a case where the distance of the gap 14 is 1 mm, He gasis supplied to the gap 14 and the gas pressure is controlled to 10 Torr;and, when the heat input to the inner cylinder 6 is 0 to 300 W, thetemperature of the inner cylinder 6 can be kept in 150° C.±20° C. for anouter cylinder temperature of 150° C.

An optimum temperature for the inner cylinder differs depending on acombination of factors, including the kind of inner cylinder, the filmquality to be processed, the kind of process gas being used, thedischarge condition and so on.

In a case where, for example, a resist attached oxide film sample asshown in FIG. 12 is processed by using a CF family gas as the processgas and quartz as the material for the inner cylinder, when thetemperature of the inner cylinder is not controlled, the temperature ofthe inner cylinder gradually increases as it receives heat from theplasma and eventually levels off to a certain temperature as the numberof processed samples is increased, as shown in FIG. 13. Therein,although the change in the etching speed of the oxide film is small, theetching speed of the resist gradually decreases as the temperature ofthe inner cylinder increases and then the etching speed of the resist isstabilized when the temperature of the inner cylinder becomes saturated.

On the other hand, by maintaining the temperature of the inner cylinderat the saturating temperature of FIG. 13 in advance, a stable etchingspeed for the resist can be obtained from the first sheet of theprocessed samples.

In a case where the temperature of the inner cylinder is continuouslybeing kept at an initial temperature, not at the saturating temperatureshown in FIG. 13, the etching speed for the first sheet of the processedsamples can be obtained.

The heat transfer capability of the gap is higher when the gap 14 isnarrower, but the effect needed for the required temperature control canbe achieved up to a gap of 2 mm.

The material of the inner cylinder 6 in this embodiment needs to be anon-magnetic material because of the microwave discharge using amagnetic field, and it should have the property that its quality willnot be varied by plasma and it should not contain any heavy metals. Asmaterials satisfying these conditions, there are carbon (C), silicon(Si), quartz (SiO), alumina (Al₂O₃) and so on. However, aluminum may beemployed depending on the content of the plasma processing.

The inner cylinder 6 is required to have a mechanical strength above acertain value and durability. That is, the SiC cylinder forming theinner cylinder 6 in the embodiment must have sufficient a thickness tohave a mechanical strength capable of withstanding an outer force actingduring plasma processing, and it has to have a durability capable ofwithstanding a large amount of wafer processing while it is worn byplasma.

On the presumption that the SiC wall is worn at the rate ofapproximately 0.05 μm every minute by etching and the practical numberof wafers processed by one inner cylinder is several ten thousands, anSic wall thickness of 2 to 10 mm is sufficient.

In the embodiment shown in FIG. 1, it is preferable on the surfacetemperature of the quartz plate 3 to be also controlled to 100° C. to350° C. in the same manner as the temperature control of the innercylinder 6.

FIG. 5 is a vertical cross-sectional view showing another embodiment ofa microwave plasma processing apparatus in accordance with the presentinvention. The process chamber 4 is constructed with an outer cylinder 5formed of a highly pure aluminum and an inner cylinder 6 formed of aceramic and arranged within the outer cylinder. The inside surface ofthe process chamber 4 is reversely taper shaped, and the inner cylinder6 is truncated cone shaped. There is a gap 14 between the outer cylinder5 and the inner cylinder 6. In the gap 14, a corrugated plate 30 made ofaluminum is arranged, and the corrugated plate 30 contacts the outercylinder 5 and the inner cylinder 6 with a spring force, as seen in FIG.6. A heater 21 for heating is arranged around the periphery of the outercylinder 5. The lower portion of the inner cylinder 6 is supported on asupport member 32 through a spring 31. There is also a spring 33 in theupper portion of the inner cylinder 6. The contact force between theouter cylinder 5 and the inner cylinder 6 is increased by these springs31, 33 and the corrugated plate 30. The springs 31, 33 also have afunction to absorb any difference of thermal expansion between the outercylinder 5 and the inner cylinder 6.

In this embodiment, the function of the inner cylinder 6 formed of SiCis the same as that in the previous embodiment. This embodiment ischaracterized by the fact that heat transmission between the outercylinder 5 and the inner cylinder 6 is performed by a combination ofcontact heat transmission by the corrugated plate 31 and gas heattransmission by the gas inside the gap 14. According to the embodiment,the etching characteristic can be stabilized since the surfacetemperature 52 of the process chamber, that is, the temperature of theinner cylinder 6, can be kept at a temperature close to the temperatureT₀ of the outer cylinder 5.

In the embodiments in FIG. 1 to FIG. 5, the temperature of the innercylinder 6 may be detected indirectly, if it cannot be detecteddirectly. However, the following effects can be obtained by attaching atemperature detector 23 to the inner cylinder 6.

(1) By making the pressure in the gap 14 variable or by finely adjustingthe temperature of the outer cylinder 5 in order to control thetemperature of the inner cylinder 6 more accurately, controllability ofthe inner cylinder temperature can be improved.

(2) By monitoring the temperature of the inner cylinder 6, it ispossible to output an alarm signal, such as to indicate the need forstopping plasma processing or to quit plasma processing when thetemperature of the inner cylinder 6 exceeds a preset range.

In the embodiments in FIG. 1 to FIG. 5, a heater is used as thetemperature control function for the outer cylinder. However, byrecirculating a temperature controlled liquid to the outer cylinder, itis possible to widen the temperature control range from a cooled statebelow room temperature to a heated state, and accordinglycontrollability of the inner cylinder temperature can be improved inthis way.

FIG. 7 shows another embodiment of a parallel plate plasma etchingapparatus to which the present invention is applied. This apparatus hasa vacuum chamber serving as a process chamber 4, which is asubstantially closed metallic reaction chamber 40 constructed by anupper plate 41, a side wall 42 forming an outer cylinder and a bottomplate 43. In the vacuum chamber there is provided a pair of parallelplate electrodes facing each other, the anode 41 being grounded to theinside wall of the chamber 40 and the cathode 47 being mounted on thechamber 40 through an insulator 46, and there is also provided a highfrequency power source 48 for supplying high frequency energy to thecathode 47. Further, there are provided a vacuum pump connecting part 44for partially evacuating the process chamber 4 and a reaction gas supplysource for supplying a reaction gas to the process chamber 4 through avalve controlled pipe 45. A wafer 11 to be etched is mounted on thecathode 47.

An inner cylinder 49 made of SiC is formed on the inside surface of thechamber 40, that is, on the upper plate 41, the side wall 42 and thebottom plate 43. There is a gap 50 between the side wall 42 and theinner cylinder 49, and a heat transfer gas for temperature control isintroduced in the gap from a gas supply system. The gas supply systemhas a gas source, a pressure control valve, a pressure detector, apressure command instruction means and a controller, and operates so asto maintain the pressure P in the gap 50 at a preset value, in the samemanner as in the embodiment of FIG. 1. A heater 51 for heating theprocess chamber 4 is arranged around the outer periphery of the chamber40, and the temperature T₀ of the side wall 42 is controlled by atemperature controller through the heater 51 and the temperature T ofthe inner cylinder 49 can be kept to a desired value, as described inthe embodiment of FIG. 1. A temperature detector 23 may be attached tothe inner cylinder 49.

With such a construction, by maintaining the temperature of the innercylinder 49 at a preset value during plasma etching, it is possible toobtain the effect that the metal is not worn nor is its quality variedby the plasma in the same manner as in the embodiments described above.Further, since the inside surface of the inner cylinder 49 is alwaysrenewed to a new surface, there is no worry about contamination due tovariation in the quality of the inside surface. Furthermore, since thetemperature of the inner cylinder 49 is maintained at a preset value, itis possible to carry out a stable plasma processing. Herein, in the caseof a parallel plate type etching apparatus, it is not necessary to limitthe material of the inner cylinder to a non-magnetic material.

The present invention can be applied to other apparatuses havingdifferent plasma generating mechanisms. Examples of such applicationsare shown in FIG. 8 to FIG. 11.

FIG. 8 shows an example of a magnetron RIE apparatus having a magnetron80 to which the present invention is applied. A process chamber 4 of avacuum chamber has a side wall 42, a sample table 10 for mounting awafer 11 and a high frequency power source 48 for supplying highfrequency energy to the electrode of the sample table 10. Further, thereare a connection part to a vacuum pump for partially evacuating theprocess chamber 4 and a reaction gas supply source for supplying areaction gas to the process chamber 4 through a valve controlled pipe13.

An inner cylinder 49 made of SiC is disposed inside of the chamber 4adjacent the surface of the side wall 42. There is a gap between theside wall 42 and the inner cylinder 49, and a heat transfer gas fortemperature control is introduced in the gap from a gas supply system15. The gas supply system has a gas source, a pressure control valve, apressure detector, a pressure command instruction means and acontroller, and operates so as to maintain the pressure P in the gap 50at a preset value, in the same manner as in the embodiment of FIG. 1. Aheater 51 for heating the process chamber 4 is arranged around the outerperiphery of the side wall 42, the temperature T₀ of the side wall 42being controlled by a temperature controller 22 through the heater 51 sothat the temperature T of the inner cylinder 49 can be kept to a desiredvalue, as described in the embodiment of FIG. 1.

With such a construction, by maintaining the temperature of the innercylinder 49 at a preset value during plasma etching, it is possible toperform a stable plasma processing in the same manner as described inthe above embodiment. Further, it is possible to obtain the effect thatthe metal is not worn nor varied in quality by the plasma. Further,since the inside surface of the inner cylinder 49 is always renewed to anew surface, there is no worry about contamination due to variation inthe quality of the inside surface.

FIG. 9 shows an example of a plasma processing apparatus to which thepresent invention is applied, the plasma processing apparatus being ofan external energy supplying discharge type, and particularly of aninduction coupling discharge type and a non-magnetic field type. Aprocess chamber 4 is formed by a silicon plate 90 and a quartz chamber92. The reference character 91 denotes a heated antenna member and thereference character 95 designates an upper heater. In this embodiment,by maintaining the temperature of the quartz chamber 92 at a presetvalue during plasma etching, it is possible to perform a stable plasmaprocessing by the same action described in the above embodiment.Further, it is possible to obtain the effect that the metal is not wornnor varied in quality by the plasma. Further, since the inside surfaceof the quartz chamber 92 is always renewed to a new surface, there is noworry about contamination due to variation in the quality of the insidesurface.

FIG. 10 shows an example of a plasma processing apparatus to which thepresent invention is applied, the plasma processing apparatus being ofan external energy supplying discharge type, and particularly of aninduction coupling discharge type and a magnetic field type. Thereference character 105 denotes a bell jar and the reference character110 designates an antenna. A process chamber 4 of a vacuum chamber hasan inner cylinder 112, an outer cylinder 114, a sample table 10 formounting a wafer 11 and a high frequency power source 48 for supplyinghigh frequency energy to the electrode of the sample table 10. Further,there are a connection part to a vacuum pump for partially evacuatingthe process chamber 4 and a reaction gas supply source for supplying areaction gas to the process chamber 4 through a valve controlled pipe.Furthermore, there are provided a heater 116 and a cooling water passage120 for performing temperature control by heating and cooling the outercylinder 114.

There is a gap between the inner cylinder 112 made of SiC and the outercylinder 114, and a heat transfer gas for temperature control isintroduced in the gap from a gas supply system 15. The gas supply systemhas a gas source, a pressure control valve, a pressure detector, apressure command instruction means and a controller, and operates so asto maintain the pressure P in the gap at a preset value. The temperatureT₀ of the outer cylinder 114 is controlled by a temperature controllerthrough the heater 116 and the temperature T of the inner cylinder 112can be kept to a desired value.

With such a construction, by maintaining the temperature of the innercylinder 112 at a preset value during plasma etching, it is possible toperform a stable plasma processing by the same action described in theabove embodiment. Further, it is possible to obtain the effect that themetal is not worn nor varied in quality by the plasma. Further, sincethe inside surface of the inner cylinder 49 is always renewed to a newsurface, there is no worry about contamination due to variation in thequality of the inside surface.

FIG. 11 shows an example of a plasma processing apparatus to which thepresent invention is applied, the plasma processing apparatus being ofan external energy supplying discharge type, and particularly of aninduction coupling discharge type and a magnetic field type. Thereference character 120 denotes an electrode and the reference character48 designates a high frequency power source. A process chamber 4 of avacuum chamber has a ceramic plate 124, an inner cylinder 122, and asample table 10 for mounting a wafer 11. Further, there are provided aheater 166 and a gas flow passage 130 for supplying a gas to the gap toperform temperature control by heating and cooling the ceramic plate124. A gas supply system has a gas source, a pressure control valve, apressure detector, a pressure command instruction means and acontroller, and operates so as to maintain the pressure P in the gap ata preset value. The temperature T₀ of the ceramic plate 124 iscontrolled by a temperature controller through the heater 126 and thetemperature T of the inner cylinder 122 can be kept to a desired value.

With such a construction, by maintaining the temperature of the innercylinder 122 at a preset value, it is possible to perform a stableplasma processing by the same action described in the above embodiment.Further, it is possible to obtain the effect that the metal is not wornnor varied in quality by the plasma. Further, since the inside surfaceof the inner cylinder is always renewed to a new surface, there is noworry about contamination due to variation in the quality of the insidesurface.

In each of the embodiments described in FIG. 8 to FIG. 11, it ispreferable that a non-magnetic and non-metallic material be used for thematerial of the inner cylinder in order to decrease the effects of themagnetic field and the electric field.

The present invention can be applied not only to a plasma etchingapparatus but also to a CVD apparatus or a spattering apparatus.Further, application of the present invention is not limited to the casewhere a process is stabilized by maintaining the temperature of theinner cylinder to a preset value. The present invention can be alsoapplied to, for example, a case where an initial process change for alot is corrected by intentionally changing the temperature of the innercylinder at the initial stage of the lot. That is, it is possible tostabilize a process by improving the temperature controllability for theinner cylinder.

The apparatuses described in FIG. 1 to FIG. 11 are used as follows.

Before starting operation of the apparatus, it is checked to determinewhether or not the temperature of the inner cylinder can be controlledto a desired temperature.

Firstly, the inside of the process chamber 4 is evacuated to a presetpressure by action of the vacuum pump. Then, the heater is operated. Theinner cylinder is heated by heat generation of the heater. During thisperiod, a heat transfer gas is supplied to the gap and the gas pressurein the gap is adjusted to a preset pressure. That is, heating of theinner cylinder is performed by utilizing heat transfer of the heattransfer gas supplied to the gap. The temperature of the heated innercylinder is directly or indirectly detected and controlled to a desiredtemperature. By doing so, it can be confirmed that the temperature ofthe inner cylinder can be controlled to the desired temperature. If thetemperature of the inner cylinder cannot be controlled to the desiredtemperature, operation of the heater is stopped and supply of the heattransfer gas to the gap is stopped. Then, the cause of the trouble ischecked and repaired.

In the above case, one wafer is introduced into the process chamberusing a transfer machine which is not shown in the figures. Theintroduced wafer is transferred from the transfer machine to the sampletable and mounted on a sample mounting surface so that the surfaceopposite to the surface to be processed is facing the sample mountingsurface. In the apparatuses described with reference to FIG. 1 to FIG.11, a temperature control means having a cooling function is provided atthe sample table. In a CVD apparatus or a spattering apparatus whichrequires to heat a wafer during processing, a temperature control meanshaving a heating function is provided at the sample table. The wafermounted on the sample mounting surface of the sample table is held onthe sample table by a mechanical clamping means utilizing a spring forceor gravitational force, an electrostatic attracting means, a vacuumsucking means or the like.

Then, a process gas is introduced into the process chamber with a presetflow rate. A part of the process gas introduced in the process chamberis exhausted out of the process chamber by the operating vacuum pump. Bydoing so, the pressure inside the process chamber is adjusted to aprocessing pressure of the wafer.

Under such a condition, the process gas in the process chamber ischanged to a plasma by discharge. The surface of the wafer mounted onthe sample table is processed by plasma. During processing, thetemperature of the wafer is controlled at a preset temperature.

During processing, the temperature of the inner cylinder is monitoredcontinuously or when required. The monitored temperature is comparedwith a preset desired temperature, and the temperature of the innercylinder is controlled to the desired temperature based on the result ofthe comparison. The temperature control of the inner cylinder isperformed by adjusting the pressure of the heat transfer gas in the gapbetween the inner cylinder and the outer cylinder or by adjusting thetemperature of the outer cylinder by adjusting the heat being generatedby the heater. The pressure adjusting of the heat transfer gas in thegap between the inner cylinder and the outer cylinder is performed byadjusting the supply flow rate or the pressure of the heat transfer gassupplied to the gap.

In general, plural wafers are continuously processed one by one. In sucha case, the temperature of the inner cylinder is monitored whileprocessing one wafer among them until processing for the all pluralwafers is completed to control the temperature to the desiredtemperature. For example, when trouble occurs in the temperaturemonitoring of the inner cylinder or when the temperature of the innercylinder cannot be controlled to the desired temperature, it is judgedthat the processing characteristic of the wafer cannot be maintainedstable and the wafer processing is stopped. Then, an effort is made tosolve the problem, and the successive process for plural wafers isre-started.

The fact that trouble occurs in the temperature monitoring of the innercylinder or that the temperature of the inner cylinder cannot becontrolled to the desired temperature is indicated to an operator byoutput of some kind of alarm through the controller. In response to thealarm, the operator solves the trouble and re-starts the waferprocessing. By monitoring the temperature control of the inner cylinder,the history of the processing up until the stopping of the waferprocessing can be checked, and consequently the search of the cause andthe repairing method can be performed properly and fast.

A cleaning process is performed for the inside of the process chamber.The process is performed by wiping the inside surface of the processchamber, such as the surface of the inner cylinder, and the surfaces ofparts arranged inside the process chamber, such as the sample table, orby utilizing a cleaning gas plasma. The process is performed before awafer processing, in the intervals between processings, or aftercompletion of a wafer processing.

In a case of performing a cleaning process by wiping, it is checkedwhether the temperature of the inner cylinder can be controlled during aperiod after completion of the cleaning processing and before thestarting of a wafer processing. On the other hand, in a case ofperforming a cleaning process by utilizing a plasma, it is checkedwhether the temperature of the inner cylinder can be controlled duringthe cleaning processing or during a period after the cleaning processand before starting of a wafer processing.

Further, a discharge running-in (seasoning) process is performed for theinside of the process chamber. The seasoning process is performed beforestarting a wafer processing at the beginning of a day, or during aperiod after completion of a cleaning processing and before starting ofa wafer processing. In this case, it may be checked during the seasoningprocess whether the temperature of the inner cylinder can be controlledor not.

In order to stabilize the characteristic of plasma processing over time,it is necessary to control the temperature of the inner cylinder to atemperature corresponding to a wafer processing condition. Here, thewafer processing conditions include the quality of film to be processed,the kind of processing gas to be used, the condition of discharge, thetype of discharge and so on.

Therefore, wafer processing conditions are input to the controller ofthe processing apparatus from a higher level controlling unit or anoperator. The controller has received an indication of the temperatureof the inner cylinder corresponding to each of the wafer processingconditions. In the controller, the temperature of the inner cylindercorresponding to the input wafer processing condition is selected andset as a control temperature. On the other hand, a detected andmonitored temperature of the inner cylinder is input to the controller.The detected and monitored temperatures are compared with the controltemperature, and the temperature of the inner cylinder is controlled tothe control temperature based on the result of comparison.

Further, in a case where the wafer is, for example, of a multi-layerfilm structure, the temperature of the inner cylinder may be controlledto a temperature corresponding to that set for the quality of each film,the kind of process gas, the condition of discharge and so on. By doingso, the characteristic of plasma processing can be finely stabilizedover time.

In a case where a wafer processing performance is varied during one lotprocessing after a running-in discharge (seasoning) process, thetemperature of the inner cylinder may be varied along a desiredtemperature pattern in order to make the processing performance uniform.

Although the above description has been directed to the temperaturecontrol of the inner cylinder inside the chamber, the present inventioncan be similarly applied to the temperature control of the sample tablecover arranged around the sample table.

FIG. 14 is a cross-sectional view showing an embodiment of a sampletable cover portion of a plasma processing apparatus to which thepresent invention is applied. A liquid for temperature control isrecirculated inside a sample table 10, so that an insulator applied ontothe surface of the sample table will be maintained at a desiredtemperature, and a sample 11 is attracted to the sample table 10 by anelectrostatic force using an direct current power source 54 forproviding an electrostatic chuck under a condition wherein a dischargeexists in the processing chamber. A heat transfer gas, for example,helium gas is introduced between the sample 11 and the sample table 10in order to increase the thermal conductance. A sample table cover madeof an insulator, such as alumina or the like, or a resistive material,such as SiC or the like, is arranged in the upper portion of the sampletable 10 to prevent discharge of undesired metals when the metallicsample table 10 is exposed to a plasma. The temperature of the sampletable cover is raised as ions and radicals in the plasma collide withthe surface of the sample table cover 50. When the temperature of thesample table cover 50 near the sample is varied, there is a disadvantagein that chemical-physical reaction is varied, and consequently theprocessing characteristic of the sample is varied. Therefore, a gassealing means 55, for example, an O-ring, is provided between the sampletable 10 and the sample table cover 50, and a heat transfer gas isintroduced between the sample table 10 and the sample table cover 50.The pressure control and its related system are the same as in the caseof the inner cylinder. Although the heat transfer gas for cooling asample is also used for the heat transfer gas for cooling the sampletable cover in FIG. 14, needless to say, the gas may be separatelysupplied.

According to the present invention, the temperature of the innercylinder which directly contacts the plasma can be controlled, and thechange in the characteristic of the plasma processing can be controlledover time.

Further, according to the present invention, it is possible to provide aplasma processing apparatus and a plasma processing method having astable plasma processing characteristic which can avoid heavy metalcontamination caused by use of a non-magnetic and conductive metallicmaterial to form the process chamber, which is subjected to being wornand having its quality varied by plasma, and under a condition that thewall surface of the process chamber is not chemically corroded by thereaction gas used inside the process chamber.

1. A plasma processing method for plasma processing a specimen by aplasma processing apparatus including a plasma generating unit, aprocess chamber capable of having an inside pressure thereof reduced, aprocess gas supply unit for supplying gas to the process chamber, aspecimen table for holding a specimen, and a vacuum pumping unit,wherein the process chamber includes an outer cylinder having thecapability of withstanding a reduced pressure, a heater being providedfor the outer cylinder and an inner cylinder being detachably heldinside of the outer cylinder and being directly contacted by plasmagenerated during the plasma processing of the specimen, the innercylinder being made of non-magnetic material and being replaceable fromthe outer cylinder, the plasma processing method comprising: monitoringa temperature of the inner cylinder during processing of the specimen;comparing a desired inner cylinder temperature which is inputted inadvance in response to a processing condition of the specimen with themonitored temperature of the inner cylinder; and controlling the heaterto control a temperature of the outer cylinder in response to a resultof the comparison thereby indirectly controlling the inner cylindertemperature to a predetermined value.
 2. The plasma processing methodaccording to claim 1, wherein a temperature of the inner cylinder is oneof monitored continuously and optionally.
 3. The plasma processingmethod according to claim 1, wherein when a plurality of specimens areprocessed continuously one by one, the inner cylinder temperature ismonitored continuously one by one until a processing of the plurality ofspecimens is completed.
 4. The plasma processing method according toclaim 1, wherein a history of the specimen up to an interruption ofplasma processing is checked and the processing of the specimen isstarted again.
 5. The plasma processing method according to claim 1,wherein when a seasoning electrical discharging processing is carriedout in the process chamber, the temperature of the inner cylinder ismonitored during the seasoning electrical discharging processing.
 6. Theplasma processing method according to claim 1, wherein the temperatureof the inner cylinder is monitored either one of before starting aplasma processing for the specimen and after completion of a cleaningprocessing.
 7. The plasma processing method according to claim 1,wherein the plasma processing for the specimen is interrupted inresponse to a result of the monitoring.
 8. The plasma processing methodaccording to claim 1, wherein an alarm is generated in response to themonitored temperature.
 9. The plasma processing method according toclaim 1, wherein a gap for heat transfer gas is formed between the innercylinder and the outer cylinder, and the inner cylinder temperature isindirectly controlled to the predetermined value by heat transferthrough the heat transfer gas in the gap formed between the innercylinder and the outer cylinder.
 10. The plasma processing methodaccording to claim 9, wherein the inner cylinder which is made of thenon-magnetic magnetic is made of conductive material.
 11. A plasmaprocessing method for plasma processing a specimen by a plasmaprocessing apparatus including a plasma generating unit, a processchamber capable of having an inside pressure thereof reduced, a processgas supply unit for supplying gas to the process chamber, a specimentable for holding a specimen, and a vacuum pumping unit, wherein theprocess chamber includes an outer cylinder having the capability ofwithstanding a reduced pressure, and an inner cylinder arranged insidethe outer cylinder, the inner cylinder being made of non-magneticmaterial and being replaceable, the method comprising: monitoring atemperature of the inner cylinder; comparing a desired inner cylindertemperature which is inputted in advance in response to a processingcondition of a lot of the specimens with the monitored temperature ofthe inner cylinder; and controlling a temperature of the outer cylinderin response to a result of the comparison so as to correct a variationin initial processing of the lot by changing the inner cylindertemperature at the initial stage of processing of the lot.
 12. Theplasma processing method according to claim 11, wherein a temperature ofthe inner cylinder is one of monitored continuously and optionally. 13.The plasma processing method according to claim 11, wherein when aplurality of specimens are processed continuously one by one, the innercylinder temperature is monitored continuously one by one until aprocessing of the plurality of specimens is completed.
 14. The plasmaprocessing method according to claim 11, wherein a history of thespecimen up to an interruption of plasma processing is checked and theprocessing of the specimen is started again.
 15. The plasma processingmethod according to claim 11, wherein when a seasoning electricaldischarging processing is carried out in the process chamber, thetemperature of the inner cylinder is monitored during the seasoningelectrical discharging processing.
 16. The plasma processing methodaccording to claim 11, wherein the temperature of the inner cylinder ismonitored either one of before starting a plasma processing for thespecimen and after completion of a cleaning processing.
 17. The plasmaprocessing method according to claim 11, wherein the plasma processingfor the specimen is interrupted in response to a result of themonitoring.
 18. The plasma processing method according to claim 11,wherein an alarm is generated in response to the monitored temperature.19. A plasma processing method for plasma processing a specimen by aplasma processing apparatus including a plasma generating unit, aprocess chamber capable of having an inside pressure thereof reduced, aprocess gas supply unit for supplying gas to the process chamber, aspecimen table for holding a specimen, and a vacuum pumping unit,wherein the process chamber includes an outer cylinder having thecapability of withstanding a reduced pressure, and an inner cylinderarranged inside the outer cylinder, the inner cylinder being made ofnon-magnetic material and being replaceable, the method comprising:monitoring a temperature of the inner cylinder; comparing, when aspecimen having a multi-layer film structure is processed, a desiredinner cylinder temperature which is inputted in advance in response to afilm quality of each of the films of the multi-layer film structure, atype of processing gas and an electrical discharging condition with themonitored temperature of the inner cylinder; and controlling the innercylinder temperature to a predetermined value by controlling atemperature of the outer cylinder in response to a result of thecomparison; wherein the inner cylinder is detachably held inside of theouter cylinder and is directly contacted by plasma generated during theplasma processing, a heater being provided for the outer cylinder, andthe inner cylinder being replaceable from the outer cylinder, the plasmaprocessing method further comprising the monitoring of the temperatureof the inner cylinder during processing of the specimen, and controllingthe temperature of the outer cylinder by the heater in response to aresult of the comparison thereby indirectly controlling the innercylinder temperature to the predetermined value.
 20. The plasmaprocessing method according to claim 19, wherein a temperature of theinner cylinder is one of monitored continuously and optionally.
 21. Theplasma processing method according to claim 19, wherein when a pluralityof specimens are processed continuously one by one, the inner cylindertemperature is monitored continuously one by one until a processing ofthe plurality of specimens is completed.
 22. The plasma processingmethod according to claim 19, wherein a history of the specimen up to aninterruption of plasma processing is checked and the processing of thespecimen is started again.
 23. The plasma processing method according toclaim 19, wherein when a seasoning electrical discharging processing iscarried out in the process chamber, the temperature of the innercylinder is monitored during the seasoning electrical dischargingprocessing.
 24. The plasma processing method according to claim 19,wherein the temperature of the inner cylinder is monitored either one ofbefore starting a plasma processing for the specimen and aftercompletion of a cleaning processing.
 25. The plasma processing methodaccording to claim 19, wherein the plasma processing for the specimen isinterrupted in response to a result of the monitoring.
 26. The plasmaprocessing method according to claim 19, wherein an alarm is generatedin response to the monitored temperature.
 27. The plasma processingmethod according to claim 19, wherein a gap for heat transfer gas isformed between the inner cylinder and the outer cylinder, and the innercylinder temperature is indirectly controlled to the predetermined valueby heat transfer through the heat transfer gas in the gap formed betweenthe inner cylinder and the outer cylinder.
 28. The plasma processingmethod according to claim 27, wherein the inner cylinder which is madeof the non-magnetic magnetic is made of conductive material.